Support opacity in ThemableDecorationAttachmentRenderOptions

[AndreasArvidsson]

I would like to be able to set opacity in ThemableDecorationAttachmentRenderOptions

I use before/after to insert a graphic. Since unused variables have a lower opacity that also affects the inserted graphic which I don't want.

[pokey]

Did a bit of exploration here, and it seems that the problem is that when the :before pseudo-element is generated, it is wrapped in a span which also has the squiggly-inline-unnecessary class set. Because that parent has an opacity less than 1, the child :before tag cannot have an opacity of 1. But because this span wraps only the :before pseudoelement, and not any of the actual text that has been decorated, we propose not to add the squiggly-inline-unnecessary class to the span wrapping this :before pseudoelement. The text itself will remain transparent, but the before element will not

[NonsenseRemedy]

To give some context on why this issue is important:

I use the cursorless VSCode plugin to write code by voice. cursorless annotates tokens in a file with colored "hats", allowing the user to refer to them in a compact way. When these hats have reduced opacity, it becomes very challenging to distinguish between the different colors, and thus difficult to manipulate the code.

https://www.cursorless.org/

[varunreddydcsg]

Testing visibility - ignore